JP2000179956A - Vehicle air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable vehicle air conditioner wherein temperature rise of a driving section of a compressor is reduced. SOLUTION: A CPU 11a of a controller 11 detects voltage of a battery 10 repeatedly at all times, and when it becomes a threshold or lower set in a memory 11b, the control is moved to a limit mode to limit maximum output electric power of a converter 9. Thus, there are suppressed an increase of an input current following lowering of battery voltage and heating from circuit elements to improve reliability. A miniaturized article having a lower rated current is useable for circuit elements such as a semiconductor and a coil, and hence miniaturization of the converter 9 and a vehicle air conditioner can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for a vehicle, and more particularly to control for suppressing a rise in temperature of a drive section of a compressor for compressing a refrigerant in a refrigeration cycle.

[0002]

2. Description of the Related Art Generally, in a vehicle air conditioner, a compressor, a condenser, a liquid tank, an expansion valve, and an evaporator are connected by a refrigerant pipe to form a closed circuit. In this closed circuit, the refrigerant that has been pressurized by the compressor and has become high temperature and high pressure is cooled and liquefied by the condenser and then expanded by the expansion valve. A so-called refrigeration cycle is formed by refrigerant circulation in which replacement is performed and the air is cooled to become gaseous refrigerant and returned to the compressor.

In this refrigeration cycle, the compressor converts the motion of a built-in motor into a piston motion or the like to perform refrigerant compression. The motor is driven by an inverter, which receives power from a battery. If a stabilized power supply with a higher voltage than the battery voltage is required, a DC / DC converter is installed between the battery and the inverter.

[0004]

As described above, the driving section including the DC / DC converter and the inverter for driving the compressor of the conventional vehicle air conditioner supplies power from the battery to the compressor.

However, the compressor drive unit attempts to supply the electric power required by the compressor even when the battery voltage drops, so that when the battery voltage drops as shown in FIG. The input current increases. Therefore, conventionally, in order to increase the input current, the circuit element of the drive unit, particularly the semiconductor or the coil that performs the switching operation, has to be large enough to withstand a large current.

When the input current increases, the heat value increases in proportion to its square. Therefore, it is necessary to widen the interval in order to cool the components, and the driving unit has to be enlarged.

Further, a large amount of heat shortens the life of the electrolytic capacitor and coil of the driving section, leading to a reduction in reliability.

In particular, since the battery voltage of an electric vehicle fluctuates by more than ± 50% with acceleration or deceleration, there is a possibility that heat generation of the drive unit increases.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a highly reliable air conditioner for a vehicle in which a temperature rise of a driving portion of a compressor is small.

[0010]

In order to achieve the above object, an air conditioner for a vehicle according to the present invention comprises a compressor for compressing a refrigerant of a refrigeration cycle and a detection unit for detecting a power supply voltage of a drive unit for driving the compressor. Means, and output limiting means for limiting the output of the drive unit when the value detected by the detecting means is equal to or less than a predetermined value.

[0011]

According to the present invention, the detecting means detects the power supply voltage of the drive unit of the compressor, and the output limiting means detects the power supply voltage of the drive unit when the detected power supply voltage falls below a predetermined value. Since the output is limited, an increase in the temperature of the circuit element of the drive unit due to an increase in the current is suppressed, and the reliability is improved. Further, a small-sized product having a low current rating can be used for the circuit element, and the size of the vehicle air conditioner can be reduced.

In particular, in an electric vehicle in which the power supply of the drive unit of the compressor is shared with the power supply of the motor for driving the wheels, the effect that the running performance is less affected is obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vehicle air conditioner according to the present invention will be described below in detail with reference to FIGS.

FIG. 1 is a block diagram of a first embodiment of a vehicle air conditioner according to the present invention.
Are as follows.

The compressor 1 compresses low-temperature and low-pressure refrigerant, and includes a three-phase motor and a compression mechanism (both not shown). The condenser 2 converts the high-temperature vaporized refrigerant flowing from the compressor 1 into a cooling fan motor 6.
It cools and liquefies. The liquid tank 3 is for storing a liquefied refrigerant, and the pressure reducing means 4 is constituted by an expansion valve, and converts the liquid refrigerant into a low-temperature mist. The evaporator 5 cools the warm air that has flowed in or out of the vehicle interior by the blower motor 7 with the latent heat of vaporization of the refrigerant. This air becomes cooling air as shown by the arrow a, and is sent into the vehicle interior through the air duct 12. These components of the refrigeration cycle 100 are connected to the refrigerant pipe 10.
1 is connected.

The inverter 8 is a driving device for supplying three-phase pulse power to the compressor 1. Converter 9 is a DC / DC converter (stabilized power supply) that boosts battery 10 and supplies DC power to inverter 8.

The controller 11 controls the output current of the converter 9 and has a programmable CP.
U11a and a memory 11b. CPU
A voltage signal of the battery 10 is input to the input port 11a. The output port of the CPU 11a is connected to the converter 9. The controller 11 is usually provided inside the converter 9, but is illustrated separately for the sake of explanation.

Next, the operation of the first embodiment will be described.

When the air-conditioning apparatus having the above configuration is started, the converter 9 boosts and stabilizes the voltage of the battery 10 and feeds the power to the inverter 8, which operates the compressor 1 and circulates the refrigerant of the refrigeration cycle 100.

In this embodiment, the voltage of the battery 10 detected by the CPU 11a (hereinafter referred to as "battery voltage")
That. The two modes of operation, a normal mode in which the maximum output power is kept normal and a limit mode in which the maximum output power is limited, can be set.
These operation modes are switched by a program set in the CPU 11a.

Prior to the switching operation, a threshold value Vth of a battery voltage for distinguishing between the normal mode and the limited mode is preset in the memory 11b.

FIG. 2 is a control flowchart of mode switching by the CPU 11a.

First, the battery voltage is detected (S
1). Next, the threshold value Vth is read from the memory 11b (S
2). Then, a comparison between the detected value of the battery voltage and the threshold value Vth is performed (S3). Here, the detection value is equal to the threshold Vth
If it is determined to be higher (YES), the mode is switched to the normal mode (S4). On the other hand, in step S3, the detection value is equal to the threshold Vth.
If it is determined as follows (NO), the mode is switched to the restriction mode (S5). After steps S4 and S5, control is transferred to step S1, and a series of these operations are repeated.

In the first embodiment in which the operation mode is switched by detecting the battery voltage, the maximum output power and the maximum input current of the converter 9 change as shown in FIG.

FIG. 3A is a graph of the maximum output power Pmax of the converter 9 with respect to the battery voltage Vb.
FIG. 3B is a graph of the maximum input current Imax.

In the normal mode, as shown in FIG. 3A, the maximum output power Pmax of converter 9 is set to PH. This value may be set in consideration of the operating ambient temperature of the vehicle air conditioner and the capacity of the cooling device. When the battery voltage Vb drops and becomes lower than the threshold value Vth, the mode shifts to the limit mode, and the maximum output power Pmax is lower than PH.
L is set to L, and the maximum output power of converter 9 is limited.

Next, consider the maximum input current Imax of the converter 9 in the above operation. Maximum input current Imax
Is substantially equal to a value obtained by dividing the maximum output power Pmax by the battery voltage Vb (in this case, the internal loss is ignored). Therefore, the maximum input current Imax in the normal mode changes in inverse proportion to the battery voltage Vb as shown by the characteristic a in FIG.

On the other hand, the maximum output power Pma in the limited mode
x is reduced as shown in FIG. 3A, and the maximum input current I
The maximum is as shown by the characteristic b in FIG. This is lower than the characteristic c when the normal mode is maintained even when the battery voltage decreases.

FIG. 4 shows that the maximum output power Pmax is 100%
Battery voltage V when stepwise changed from
6 is a graph showing a relationship between b and a heat value P in the converter 9.

If the threshold voltage Vth is set to 80% with respect to the rated (100%) of the battery voltage Vb, the limiting mode is set at the battery voltage Vb lower than this, and the maximum output power Pmax at that time is reduced to 80% of the normal value. Voltage V
Even if b drops to 65%, the calorific value remains at the battery voltage V
It can be suppressed to P1 or less, which is the same as when b is 80% of the rating.

Therefore, in the first embodiment, even when the battery voltage Vb decreases, the output power is limited, and the input current is also limited accordingly. Is suppressed, and the reliability is improved. Further, it is not necessary to use a large-sized product having a large current rating for the circuit element, and the size of the converter can be reduced.

In the first embodiment, the maximum output power Pmax of the converter 9 in the limited mode is
Is constant (PL), the maximum input current Imax is reduced. However, in the limited mode, the maximum input current Imax is kept constant by linearly changing the battery voltage Vb and the maximum output power Pmax of the converter 9. Can also.

FIG. 5 shows a second embodiment of the vehicle air conditioner of the present invention.
9 is a graph showing characteristics of the converter according to the embodiment. FIG. 7A shows the characteristic of the maximum output power Pmax.
FIG. 3B shows the characteristics of the maximum input current Imax.

In the normal mode of this embodiment, FIG.
As shown in (a), the maximum output power Pmax is set to PH. Then, as in the first embodiment, FIG.
By the control method shown in the above, the battery voltage Vb is detected,
When the detected value is equal to or less than the predetermined threshold Vth, the mode is switched to the restriction mode.

In the limited mode, the maximum output power Pm
ax has a linear characteristic with respect to the battery voltage Vb. That is, when the battery voltage Vb decreases, the maximum output power Pma
x also decreases linearly similarly. This maximum output power P
The calculation for calculating max is performed by the CPU 11a.

In the second embodiment in which such control is performed, as shown in FIG. 5B, in the limit mode, the maximum input current Imax can be made substantially constant regardless of the battery voltage Vb. . Characteristic c is, for comparison,
This shows the characteristics in the case where the normal mode is maintained even when the battery voltage Vb decreases, and it can be seen that the maximum input current Imax is reduced in the limited mode of this embodiment. Therefore, also in the second embodiment, as in the first embodiment, the temperature rise of the circuit element of the converter is suppressed, the reliability is improved, and the size can be reduced.

Further, the battery 10 is connected without using a converter.
Is directly connected to the inverter 8, by limiting the maximum output power Pmax to the inverter 8, heat generation from a circuit element such as a semiconductor element used for switching in the inverter can be suppressed. Can be.

In the embodiment described above, the CPU
Although the maximum output of the converter is limited by software using, the circuit can be configured using hardware.

In this case, the threshold voltage and the battery voltage are compared by a comparator instead of the CPU 11a, and the output is amplified and input to a converter or an inverter to limit the maximum output.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a vehicle air conditioner according to a first embodiment of the present invention.

FIG. 2 is a control flowchart of mode switching of the apparatus shown in FIG.

3 is a graph showing the characteristics of the converter of the device shown in FIG. 1. FIG. 3 (a) shows the characteristics of the maximum output power Pmax, and FIG. 3 (b) shows the characteristics of the maximum input current. It is.

FIG. 4 is a graph showing a relationship between a battery voltage of the apparatus shown in FIG. 1 and a heat generation amount in a converter.

FIG. 5 is a graph showing output characteristics of the vehicle air conditioner according to the second embodiment of the present invention, and FIG.
Shows the characteristic of the maximum output power Pmax, and FIG. 2B shows the characteristic of the maximum input current Imax.

FIG. 6 is a graph showing a relationship between an input current of a drive unit of a compressor of a conventional vehicle air conditioner and a battery voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Liquid tank 4 Decompression means 5 Evaporator 6 Cooling fan motor 7 Blower motor 8 Inverter 9 Converter 10 Battery 11 Controller 11a CPU 11b Memory 12 Ventilation duct 100 Refrigeration cycle 101 Refrigerant piping

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio Ohashi 5-24-15 Minamidai, Nakano-ku, Tokyo Calsonic Co., Ltd. Fuji Electric Co., Ltd. (72) Inventor Shigenori Kinoshita 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture

Claims (1)

[Claims] 1. A compressor (1) for compressing a refrigerant of a refrigeration cycle (100), a detecting means (11) for detecting a power supply voltage of a drive section (8, 9) for driving the compressor (1), An air conditioner for a vehicle, comprising: an output limiting unit (11) for limiting an output of the driving unit (8, 9) when a value detected by the detecting unit is equal to or less than a predetermined value.